1. Technical Field
The present invention relates to a method of calculating an invoice amount for inkjet printer use, a device that calculates the invoice amount, and a printer invoicing system.
2. Related Art
Billing methods that issue invoices according to the amount of ink used by an inkjet printer are known from the literature. See, for example, Japanese Unexamined Patent Appl. Pub. JP-A-2002-36582. Some inkjet printers use an optical sensor to measure the amount of ink remaining in the ink tank, and calculate how much ink was used (ink consumption) based on the remaining amount of ink. A host computer connected to the inkjet printer gets the ink consumption information from the inkjet printer, and sends data related to ink consumption over a network to a service center server. The service center server refers to an ink volume price table, calculates the invoice amount based on actual ink consumption, and generates a bill that is sent to the user.
Inkjet printers commonly perform maintenance operations such as head cleaning and flushing (waste ejection) in order to prevent ink coagulation and to expel bubbles from the printhead or ink path. As a result, when calculating ink consumption based on the amount of ink remaining in the ink tank as described in JP-A-2002-36582, the calculated invoice amount includes not only the amount of ink used for printing (“actual print volume” below), but also the amount of ink used for printhead maintenance (“maintenance volume” below). This means that the billed customer must also pay for ink that is used for operations other than actual printing, leading to customer dissatisfaction.
Methods of calculating the invoice amount based only on the actual print volume are also conceivable. This involves some method of measuring the actual print volume and then calculating the invoice amount based on the product of the actual print volume and the ink price. For the customer, this eliminates the sense of being disadvantaged by paying for ink used for maintenance and provides the added merit of enabling easier budgeting because the amount invoiced for actual printing is clear. However, because inkjet printers require maintenance as described above, ink is also consumed when not printing. The amount of ink used for maintenance therefore increases relative to the actual print volume in the case of customers with low volume printing needs, reducing the amount invoiced relative to total ink consumption and making this business model not viable for the ink supplier that issues the invoices. As a result, a business model that calculates the invoice amount based only on the actual print volume is only applicable to large customers with high print volumes, and applying this business model to customers with low print volumes is not practical at present.